1. Field of the Invention
This invention relates to a method and apparatus of supplying fuel in an electronic control fuel injection engine for controlling the supply of fuel from a fuel injection valve to an intake system by operating the fuel injection valve according to electric signals and more particularly to a method and apparatus of supplying fuel for controlling the rotational frequency of an engine when fuel cut-off is completed and then fuel supply is resumed.
2. Description of the Prior Arts
In an electronic control fuel injection engine, it is well known to cut off fuel in the deceleration of a vehicle for improving efficiency of fuel consumption and restraining amount of purge of noxious components. When rotational speed of the engine is lowered to a predetermined value or less, fuel needs to be cut off completely and then supplied again for avoiding the stoppage of the engine rotation (engine stop). However, when the fuel supply is resumed, the output torque of the engine is abruptly increased, unbalance between the output torque of the engine and torque of driving wheels gives impact to the vehicle. In prior method and apparatus of supplying fuel to electronic control fuel injection engines, the rotational speed of the engine at the resumption of fuel supply could not be set to a small value to avoid the impact to the vehicle at the resumption of fuel supply after the completion of fuel cut-off so that the improvement of efficiency of fuel consumption during the deceleration and the restraint of purge of noxious components could not be sufficiently achieved. Also, a fuel supplying method has been proposed in which the rotational speed of the engine at the resumption of fuel supply is changed over from a large value to small one to increase a period of fuel cut-off when the transmission at the deceleration is changed over from the high speed stage to the low speed one. However, in this method, the impact at the resumption of fuel supply can not sufficiently restrained.